Blocks Blossom From Waste Wood

ByPeter Tonge, Special to The Christian Science MonitorMay 13, 1992

BOSTON
— WHEN James Bancroft shows visitors the attractive new barn cum studio he built behind his home in rural Cumberland county, New Jersey, he likes to tell them that it's "the best looking pile of waste wood chips you ever saw." It's also, he hopes, the forerunner to a lot of high-quality, low-cost housing around the country.

That's because the studio was built with wood-fiber-concrete blocks so simple to use that people with no construction skills can readily erect the basic structure. In fact, the aim of Community Innovations, the nonprofit organization he founded, is to get unskilled inner-city youths involved in building inexpensive housing right where it's needed most. Because waste wood can easily become the principal ingredient of the blocks, the system could alleviate a solid-waste disposal problem at the same time.

Conventional wisdom has it that wood fibers and concrete do not mix well because the sugars, tannins, and oils in wood prevent it from bonding properly with the concrete. In addition, wood particles decay if exposed to moisture for a long period.

But decades ago, Swiss and Austrian scientists developed a process that coats wood particles with a mineralizing seal so they bond readily with cement, sand, and stone. Wood is more expensive in Europe than it is in North America, and this prompted the development. "It was too expensive to just throw away or burn," explains Hansrudi Walter, of Faswall Concrete Systems in Augusta, Ga., which brought the system to the United States.

The system, adapted slightly to accommodate the higher sugar content in some American trees, uses naturally occurring minerals mined in the US to treat the wood. "There are no harsh chemicals involved," Mr. Walter insists, contending that "the process is really very simple when you know how."

Having both the product and the process "environmentally acceptable," pleases Mr. Bancroft, who heads Community Innovations in Bridgeton, N.J. But he's principally drawn to wood-fiber concrete because it's "so easy to use." Apart from its light weight (less than half that of conventional concrete), it can be "sawed, nailed, or screwed like any piece of wood," he says.

Take his barn cum studio. On the first day, two individuals with no masonry experience "put up a four-foot base wall around the perimeter in just two hours."

While a variety of wood-fiber concrete building products are being turned out at the Windsor, S.C., plant of Faswall Concrete Systems, Bancroft used basic blocks that are 36 inches long, 12 inches high, and 9 inches deep.

Weighing only 39 pounds, the interlocking blocks were dry-stacked to a height of four feet and a liquid concrete was then poured into the hollow centers to bind the structure into a solid wall. Another option would be to apply a thin layer of surface bonding on each side of the wall, which would weatherproof the wall at the same time.

Bancroft finished his studio walls with vinyl siding, but "the cheapest way to give a finished look is to apply stucco," he says.

Because the blocks are primarily wood fiber with some fine sand and cement to provide the bonding, the blocks are highly porous. In fact the blocks are roughly 40 percent air, which gives them an insulating value of R11. In other words they conduct heat out of the home (or into it on hot summer days) very slowly. This improves to R19 when the hollow centers are filled with poured concrete, with its high heat-storage capacity.

So "these houses are cheap to heat and cool," Bancroft says, and insurance costs would be relatively low because "walls built of these blocks have a four-hour fire rating." In other words it would take a constantly burning fire four hours before it could burn through the wall. The concrete blocks do not support combustion on their own. Another plus, the walls make the buildings "remarkably quiet and peaceful," Bancroft says. In fact, one early use of this technology in the United States was as highway so und barriers.

Tests in several tropical countries including Sri Lanka, the Congo, and Morocco show that the blocks are untroubled by termites and highly resistant to rot.

Currently, the wood-fiber blocks are being made at only one location. But the idea is to license this technology to any interested parties though businesses already involved in the precast concrete industry would be in the best position to take advantage of the technology.

While blocks, panels, and other forms can be manufactured from virgin timber and still be competitive, Walter hopes that waste wood will be the principal source of raw material as it is in Europe. Wood pallets, often made of oak, would be a particularly good source of fiber for the industry, he says. He also notes that "waste byproducts from the paper industry could supply all the wood fiber we need."

Bancroft learned of wood-fiber building blocks when he visited a high-rise project in Canada built by a commercial contractor. Fascinated by the possibilities, Bancroft had the barn-studio built in his own backyard to test the system for himself and specifically to see if it could be built with untrained labor.

The project confirmed that this building system could be used easily to provide strong solid housing in low-income neighborhoods. Now he is hoping that corporations or foundations will support demonstration projects in various parts of the country.